The use of anticipatory guidance (AG) to educate parents about typical child development, injury prevention, and optimal parenting has had mixed effects, in part because of the way AG is delivered to parents. One notable exception is the Baby Books Project (BB1), a randomly assigned NIH-funded intervention that embedded AG into baby books, rather than the typical handouts or physician discussion, to improve maternal and child health. BB1 proved quite effective in increasing low-income, new mothers' knowledge of child development and parenting, improving maternal self-efficacy, improving parenting beliefs and practices (reading, safety, discipline), reducing maternal stress and depressive symptoms, increasing children's language skills, and reducing the number of preventable child injuries over the first 18 months (all statistically significant effect sizes, .24-.59 sd). Given te success of BB1, the proposed application (Baby Books 2 - BB2) seeks to replicate and expand on these promising findings. Although BB1 was effective in impacting mothers and their parenting behaviors, like most interventions, it did not include fathers. We aim to test whether effects are equivalent for fathers and whether the impacts of this low-cost intervention are additive or perhaps multiplicative when both mothers and fathers are targeted. Moreover, if information about co-parenting - the way parents work together to raise their children - is included in addition to the AG typically provided at well-child visits, will the books impact the quality of the co-parenting relationship and subsequently benefit parents and their children? It is reasonable to expect that a family system intervention could have more enduring effects on children's outcomes than one focused solely on mothers. Further, providing AG through 24 months and following children to 30 months enables assessment of impacts on physical, cognitive, language, and social development that BB1 could not measure. Lastly, BB1 was provided in one region and exclusively in English. Testing the intervention in two geographical regions, in English and Spanish, allows for consideration of cultural variation in the impact of th educational baby books and increases the external validity of the findings. In the proposed project we will randomly assign 240 two-parent families to one of 4 conditions: educational books provided to (1) mothers only, (2) fathers only, or (3) both parents; and (4) non-educational books provided to both parents. In-home data collection will occur at 6-9 months (baseline) and at 18, 24, and 30 months, with supplemental phone interviews when children are 12, 15, and 21 months. Using a 4-group randomized design, this project (BB2) will test the impact of educational baby books on mothers only, fathers only, and mothers and fathers together in comparison to non-educational (i.e., visually similar but lacking educational content) baby books. With 7 waves of data collection using interviews, observations, and a retrospective medical chart audit, this project is one of the first to test differential and multiplicative effecs of targeting both parents and will provide valuable insight into a low-cost and easy-to-implement intervention for low-income children.